Study on Conversion of Existing HVAC Lines to Hybrid HVAC/HVDC Transmission Line to Increase Transmission Capacity and Efficiency

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Addis Ababa University


Ethiopia’s economy has been one of the fastest growing economy in the world with two digit figures in the last decade. Consequently, the rate of electric consumption has also been increasing very fast. A large number of new consumers has been recently connected to the grid or waiting to be connected. Infrastructure development boosted on different areas like, new country-wise railway developments, Addis Ababa light rail system, large new irrigation, new Industrial zone development and electricity export consumers. Gilgel gibe III hydropower project is one of mega project undertaken by the government of Ethiopia. The objective of the project is to enhance the hydropower generation capacity of the country through developing a plant with a capacity of 1870 MW. The project is expected to raise the present installed capacity from 2268 MW to 4138 MW. A total of 402km new 400 KV HVAC double circuit transmission line is constructed from Gibe III – Wolayita – Akaki II substation with a capacity of 1500MVA. In the near future the government is trying to finance for Gibee VI and Gibee V hydro power plant with combined capacity of 2100MW as part of a series of cascade dams on the Gibe River. The existing transmission line capacity cannot able to evacuate such power, therefore new transmission line construction is a must to evacuate power to load center, Addis Ababa. This thesis studies the technical and economic feasibility of converting existing 400KV HVAC line from Gibe III – Wolyita- Addis Ababa to Hybrid HVAC/HVDC line to upgrade the power transmission capacity. The new line will have a bipolar 500 KV HVDC as part of the whole transmission line In our study we have observed that we can increase the transmission efficiency from 1500MVA to 2.5GW. The investment cost for constructing new single circuit 400KV HVAC line about 855,978,477.20 USD. (17,958,428,451.66 Birr). The Hybrid HVAC/HVDC line costs 439,173,420.00 USD (9,200,683,149.00 Birr). This price reduction is about 416,805,057.20 USD (8,732,065,948.34 Birr). From Investment point of view, the total reduction of cost is about 49%. Considering the active power loss and corona loss of the two systems, the hybrid HVAC/HVDC line 97% efficient while HVAC system is 91%. The environmental effects like audible noise and radio interference as well as electric level is essentially under standard. It is found that the hybrid HVAC/HVDC line is found to be technically and economically feasible. Key words: Hybrid HVAC/HVDC, HVDC, HVAC, Radio interference, Audible noise, loss cost



Hybrid HVAC/HVDC, HVDC, HVAC, Radio interference, Audible noise, loss cost